For many decades, the paper industry has been practicing waste paper recycling to regenerate usable cellulosic fiber, for paper making, in processes called deinking processes. In these deinking processes, ink is removed from the waste paper pulp by a series of chemical and physical steps. In paper recycling processes, the deinking is carried out by converting the waste papers to a pulp and then contacting the pulp with specific compositions. Such composition induces swelling of the fiber and reduces reattachment of the ink particles to the fiber while, often, stabilizing the ink particles. The ink particles and other impurities from the pulp fiber are then released and separated.
In inkjet printing process, papers are often printed with water-based inks. In offset, laser and digital printing processes, different kind of inks, such as toner and electrostatic printing inks, are used. The use of these various inks often make the deinking process less efficient and more complex for achieving good results. Indeed, during offset, laser and digital printing processes, heat and/or pressure are applied to cause ink particles to fuse to paper surfaces. The resulting printing papers are thus very difficult to deink.
Nowadays, papers printed with laser and digital printing processes represent important volumes in the area of waste papers recycling. The industry is thus working on developing effective processes and chemistries that will help obtaining superior performances in deinking such waste paper slurries.